The invention relates generally to push button switches for elevators and, in particular, to a push button switch having a transparent push button illuminated from the rear by light emitting diodes.
Shown in the German design patent G 90 15 115.1 is a light element utilizing light emitting semiconductors for illuminating a push button switch. Arranged in the forward end of the push button switch is a ring shaped light conductor adjacent to a printed circuit board on which are mounted a plurality of light emitting semiconductors facing the ring conductor and the front of the push button. Upon actuation of the push button by an operator, the light emitting diodes are activated and emitted light is conducted by the ring conductor whereby a luminous ting becomes visible to the operator as an acknowledgement signal at the face of the push button. The light emitting semiconductors, also called light emitting diodes, are controlled in response to the ambient lighting by means of photosemiconductors, such that the visible luminous ring becomes brighter as the ambient light becomes brighter.
A disadvantage of the above described device is that the light emitted by the light emitting diodes is insufficient to provide a positive acknowledgement signal when the ambient illumination level is elevated. A further disadvantage is that the construction of the circuit board and the ring conductor makes the push button switch expensive to manufacture.